AUTOMOTIVE DESIGN


the very ends or whether it has support in the middle at the gland.


SPECIALISED STEELS Specialised piston rod steels have been developed specifi cally for hydraulics, such as Ovako’s Cromax 180X and Cromax 280X. Cromax 180X comes in the form of hard-chrome-plated bar and is based on a medium-carbon micro-alloyed steel. It has a minimum yield strength of 500N/mm2 thanks to careful control over the alloying mix and processing. T is compares with with 305N/mm2


for grade C45E. Higher yield strength means that the


piston rod can better withstand buckling. A designer can therefore reduce the diameter of a piston rod, cutting the weight of the entire cylinder. Alternatively, they could replace a C45E piston rod with an identical one in Cromax 180X to transmit a greater load with the same margin of safety against buckling, provided that the cylinder is dimensioned for the higher force/pressure. Engineers can compare diff erent grades of piston rod steel using a piston rod predictor that is part of the Steel Navigator tool on Ovako’s website. T e piston


rod predictor provides insight into how buckling resistance is aff ected by diff erent grades using both the AISC and ECCS methods. Engineers can use fatigue modelling to help them design dual-action piston rods. As a general rule, fatigue strength increases with the tensile strength of the rod material. Guaranteed impact toughness might also need to be considered for safety-critical applications. Other factors being alike, the higher


tensile strength of Cromax 180X provides considerably better fatigue performance than C45E. As with buckling resistance, using Cromax 180X could either enable downsizing of a piston rod or improving fatigue life with the same size of rod. Engineers also have to design for manufacture. T erefore, it’s important to consider the impact on machining and production. T e machinability of the Cromax grades has been fully tested in both turning and threading. Even though its strength and hardness are considerably higher, the steel can be processed effi ciently compared with materials such as C45E. Weldability is also important – and particularly friction welding, which is


Steels developed specifi cally for hydraulics enable higher yield strength


often used on piston rods that will be subjected to heavy loads. Engineers want to avoid brittle constituents forming in the weld heat aff ected zone (HAZ). Cromax grades are a good choice thanks


to alloy content that was developed to avoid the risk of centre segregation that could lead to embrittlement after friction welding. Together with their higher yield


strength, this makes them a good choice to help designers of hydraulic systems improve performance and downsize systems.


Mattias Awad is with Ovako. www.ovako.com


Think small


Or think big. INDOOR VEHICLE CLIMA TE


Think VehiDome TES T VehiDome – The future for testing and development of the vehicles of tomorrow


The automotive industry is faced with several challenges, where new trans portation methods, choice of fuel and engine types will change the way man will handle the need of transpor tation in the future.


The development of the future vehi cles calls for solutions where new tests and validations can be designed and where controllable


conditions secur ing repeatability can be offered 24/7 - 365 days per year.


The increasing need of climate testing in combination with seasons that becomes shorter year by year has formed a drastically increase in demand for efficient proving grounds with stable and controllable climatic conditions.


www.vehidome.com www.engineerlive.com 11


New patent for Indoor Vehicle test with controllable climate conditions.


Read all about it at: www.vehidome.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52